What is the airflow requirement for combustion in a gas furnace?

The airflow requirement for combustion in a gas furnace is to ensure that there is sufficient air available for the combustion process to take place efficiently and safely. This means that adequate combustion air can be drawn from either inside the building or from outside, depending on the system design and installation.

Using air from the inside may be suitable in well-ventilated spaces, particularly if the building is not tightly sealed. However, if a building is tightly sealed, relying solely on indoor air could create negative pressure, which might restrict adequate airflow and lead to unsafe operating conditions, such as backdrafting.

On the other hand, sourcing air from outside ensures that there is a continuous supply of fresh air, making the combustion process more effective and reducing the risk of harmful fumes being drawn back into the living spaces. This flexibility in sourcing combustion air aligns with the requirements of gas furnace operation, prioritizing safety and efficiency by allowing for adequate air intake from both sources, depending on building codes and the specific circumstances of the installation.